Keyboard switch assembly having coil spring contacts providing point contacts engagement

ABSTRACT

Keyboard having a plurality of switches that are actuated by selective keys. The keyboard is provided with a tensional, resilient member which forms a first contact of a switch that is arranged to abut a second contact, thus closing an electric circuit. Each key is provided with an actuating part disposed on either side of a stationary support and forces the first contact to engage the second contact at spaced locations to thereby cause the first contact to additionally function as a return spring for the key when the electric circuit is opened. This invention relates to a keyboard having at least one switch acted upon by a key to open and close electric circuits having leads mounted on the keyboard. The keyboard is provided with at least one tensional, resilient member forming a first contact in a switch which is arranged to be resiliently urged against a second contact in the switch, thus closing an electric circuit.

United States Patent [191 Anderson Dec. 16, 1975 [75] Inventor: Leif Helmer Andersson,

Atvidaberg, Sweden [73] Assignee: Facit Aktiebolag, Atvidaberg,

Sweden [22] Filed: Nov. 5, 1974 [21] Appl. No.: 521,100

[30] Foreign Application Priority Data Nov. 7, 1973 Sweden 73150955 [52] US. Cl 200/5 R; 200/159 R; 200/276 [51] Int. Cl. HOIH 13/28 [58] Field Of Search 200/5 R, 5 A, 5 E, 5 EA, 200/159 A, 262, 264, 276, 295, 340, 159 R, 159 B [56] References Cited UNITED STATES PATENTS 2,573,895 11/1951 Evett 200/276 UX 2,630,503 3/1953 Larsen et a1. 200/276 X 2,931,877 4/1960 Henley 200/262 3,226,494 12/1965 Hartz et a1. 200/295 X 3,369,097 2/1968 Murakami 200/262 3,392,250 7/1968 Ziegler et 31.... 200/159 A 3/1969 Soprani 200/276 X 3,697,706 10/1972 Huggard 200/276 X 3,735,058 5/1973 Berry t t 200/276 X 3,743,798 7/1973 Pentecost... 200/276 X 3,745,269 7/1973 Arvai 200/276 X Primary Examiner-James R. Scott Attorney, Agent, or FirmAlfred E. Miller [57] ABSTRACT Keyboard having a plurality of switches that are actuated by selective keys. The keyboard is provided with a tensional, resilient member which forms a first contact of a switch that is arranged to abut a second contact, thus closing an electric circuit. Each key is provided with an actuating part disposed on either side of a stationary support and forces the first contact to engage the second contact at spaced locations to thereby cause the first contact to additionally function as a return spring for the key when the electric circuit is opened.

This invention relates to a keyboard having at least one switch acted upon by a key to Open and close electric circuits having leads mounted on the keyboard. The keyboard is provided with at least one tensional, resilient member forming a first contact in a switch which is arranged to be resiliently urged against a second contact in the switch, thus closing an electric circuit.

9 Claims, 5 Drawing Figures U.S. Patent Dec. 16,1975 Sheet 1 Of2 IIIIIIIIHL Illlllllllly HHIIIIHHIIIII mmlllIlII/Ilm IIIIIIIIIIIHII/Ilr IIIIIIIIIIIII nIIlIIIIIHIln/n IIIlnIm/Mn IHIIIIIIHIHII IIIIIIIIIIIIIIIII/ lmlnuunm IIIIIIIIIIII 'IIIIIIIIII 'HIIIIHIIII IIIIIIIIIIII) mull"! Fig.2

Fig. 5

KEYBOARD SWITCH ASSEMBLY HAVING COIL SPRING CONTACTS PROVIDING POINT CONTACTS ENGAGEMENT BACKGROUND OF THE INVENTION A Keyboards with key-operated switches are known; however, it is generally desired to construct and arrange the keyboard in a manner so as to provide a compact,- inexpensive structure. In this regard, the contacts must be designed for a minimum of contact bounce. Furthermore, the contacts should be self-cleaning in order to avoid contact failure due to oxidation. In addition, there must be good reliability with respect to repeated contact closure.

4 The present invention satisfiesall theabove requirements.

It is anobject of the present invention to provide a uniquekey-operated switch in which one of the members. of the switch serves as a return spring for the key when the electric circuit is opened,-thus resulting in a keyboard construction having relatively few moving Another object of the present invention is to provide a modification in which the second o'rlower contact is a fixed contact rod of a smaller diameter than the tensionalfresilient second switchfmemb'er, and in which the first resilient switch member is designed to slide therealong.

The invention will now be more fully described with reference to the accompanying drawings in which:

FIG. 1 is a bottom perspective view of the keyboard housingand associated structure with the first and second switchj'rneans, as well as two keys shown detached from the housing.

FIG. 2 is a cross-sectional view of two representative keys, switches and associated structure.

FIG. 3 is a plan view of only the first and second contact means showing their positional relationships.

FIG. 4 is a cross-sectional view showing a modification of the invention in which the switch means are shown formed of an electrically conductive flexible material, and

FIG. 5 is another cross-sectional view of a further modification of the invention in which one of the contact members is a fixed contact rod.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring to FIG. 1, a casing is shown having structural members in the form of guides 11 depending downwardly from an upper plate 14 of the casing 10 and adjacent to the respective openings 13 in the plate. Thus, the keys 12 are adapted for insertion in each of the openings 13 and are preferably fabricated of a plastic material. As particularly seen in FIGS. 1 and 2, each of the keys 12 is provided with a depending skirt having lateral projections 15 that are adapted to snap under the adjacent bottom surface of upper plate 14, and

slide along the guides 11 when the key is depressed. Therefore, each of the keys 12 is movably supported within the guides 11 and are retained therein by means of projections 15. As seen in FIGS. 1 and 2, the guides 11 are provided with bars 16. Moreover, each of the keys 12-are provided with inverted V-shaped notches 17 so that when'the key is depressed it moves downwardly until the upper edges of notches l7 engage an adjacent part of bar '16 thereby forming a limiting stop.

FIGS. 1 and 3 show that the contact means for the keyboard are tension springs 18 and 19 having hooks 20 and 21 secured at their respective ends. As seen in FIG. 3,'the springs 18 and 19 are positioned substantially perpendicular to each other. Furthermore, with reference to FIG. 1, the contact springs 18, in their idle position, rest in the arcuate recesses 22 of the guide 11 with the upper surfaces engaging the bottom surfaces of bars 16, as seen in the left hand side of FIG. :2. Moreover, in this condition the spring 19 abuts against a top surface of a corresponding bar 16 since the upper edge 23 of a further notch 24 of the key 12 urges-the spring 19 in a downward direction.

It should be apparent that each contact spring 18 and 19 together form a switch in which electrical circuits operatively connected to the keyboard can be opened or closed. As seen in FIG. 1, the electrical circuitsare connected by lead wires 25 and 26 to the respective springs, the latter functioning as contact means. The wires 25 and 26 are shown soldered to the respective hooks 20 and 21, which aresecured to bars 27 of the casing 10. If the wires are in the form of -a printed circuit (not shown) the springs 18 and 19 can be attached directly to the circuit board or contact pins connected thereto. g

As seen in FIG. 4, it is possible to use other tensional, resilient means within the teachings of the present invention. Thus, instead of the-tensionsprings l8 and 19 shown in FIGs. 1 3, and described hereinbefore, elongated rods 30 of electrically conductive flexible material, such as electrically conductive rubber, are shown. Furthermore, another arrangement is envisioned. As seen in FIG. 5, the contact spring 19' remains the same as that shown in FIGS. 1 '3 while the contact spring 18 is eliminated and a fixed contact rod 32 is substituted. It should be noted that the diameter of the contact rod 32 is smaller in cross-section than that of spring 18 shown in FIG. 2, so that during the downward movement of key 12, the spring 19 slides along the contact rod 32.

The keyboard with its multiplicity of key-operated switches operates in the following manner, with particular reference to FIG. 2: In the left hand side of FIG. 2, the key-operated switch is shown with the contact in an off position. The edges 23 of the notches 24 in the switch key urge the tension spring 19 downwardly upon depression of the key 12, and into engagement with the top surface of the bar 16 so that spring assumes the curved shape shown therein. The tension spring 18 is shown extending perpendicular to the spring 19 and abuts the underside of bar 16. It will be noted that there is a substantial spacing between the two contact springs, 18 and 19 respectively.

When the key 12 is depressed, as seen in the right hand side of FIG. 2, the spring 19 comes in contact with the spring 18 after a small movement downwardly of the key. The movement is preferably in the range 1 mm. The contact is made and the circuit is closed. Thereafter, the continued movement downwardly of 3 the key 12 will cause the spring 18 to also move downwardly whereby the springs 18 and 19 will slide against each other thereby automatically cleaning the contact area.

As seen in the right hand side of FIG. 2 contact is made between springs 18 and 19 at least at two points 28 and 29. However, sincethe springs 18 and 19 are of the coil type, the turns are separatedwhen the springs are stretched at each of the contact points 28 and 29 thereby resulting in four contact points being obtained.

When the key-12 shown in the right hand side of FIG. 2 is released it returns automatically to the position shown in the left hand side of FIG. 2, inasmuch as spring 19 functions as a return spring for the key. When the key 12 returns to its idle position an excellent damping of the spring 19 is achieved because of the relative positions of the upper edges 23 of the notches 24 and the bars 16 relative to the spring 19. Under test, no contact bouncing was observed when closing the contact, and only a small amount of bouncing was observed upon opening the contact.

The excellent characteristics of the present keyboard construction permits a saving in material costs. For example, the tension springs 18 and 19 can be fabricated of stainless steel. Moreover, another advantage of the present construction is that the spring 19 which is stretched over the bar 16 during the downward movement of the key 12 is at an angle of approximately 45 to the direction of movement of the key. This arrangement results in the spring being stretched considerably less than the corresponding movement of the key, and thus the key is very conveniently operated by the user.

What is claimed is:

1. The combination of a keyboard, a key-operated switch and an electrical circuit comprising at least one elongated resilient member forming a first switch contact, an elongated second switch contact positioned substantially perpendicular to said first switch contact, a stationary support located adjacent to and over said second switch contact, a generally rectangularshaped key provided with a pair of notches on one set of opposed sides of said key and when said key is depressed the upper edges of each of said pair of opposed notches engage said first switch contact on opposite sides of said stationary support and stresses said first switch contact thereagainst whereby the first switch contact is forced into engagement with said second switch contact at two spaced points to thereby close said electrical circuit, said first switch contact additionally functioning as a return spring for said key when the electrical circuit is open.

2. The combination as claimed in claim 1 wherein said first and second contacts are secured within said keyboard, the latter having a plurality of openings provided with guides for respective corresponding keys, said guides provided with support members for said second switch contact and having said stationary support against which said first switch contact rests.

3. The combination as claimed in claim 1 further comprising another pair of notches on the other set of opposed sides of said key which are deeper than the first pair of notches whereby when said key is depressed said first switch contact is forced by said first pair of notches into engagement with said second switch contact and the upper edges of said second set of deeper notches travels further downward until said stationary stop is abutted to form a stop for the downward movement of said key.

4. The combination as claimed in claim 1, wherein the second switch contact is constituted by a second resilient member.

5. The combination as claimed in claim 1, wherein said second switch contact is a fixed contact rod.

6. The combination as claimed in claim 1, wherein said first and second contacts are positioned substantially perpendicular to each other.

7. The combination as claimed in claim 4, wherein said first and second contacts are secured within said keyboard, and the latter is provided with a plurality of openings for a plurality of corresponding keys.

8. The combination as claimed in claim 7, wherein said openings are provided with guides for the respective keys, said guides having first support members for said second switch contact and additionally being provided with second support members against which said first switch contact rests.

9. The combination as claimed in claim 8, wherein the keys are each provided with lateral projections that snap into the adjacent guide thereby being movably retained therein. 

1. The combination of a keyboard, a key-operated switch and an electrical circuit comprising at least one elongated resilient member forming a first switch contact, an elongated second switch contact positioned substantially perpendicular to said first switch contact, a stationary support located adjacent to and over said second switch contact, a generally rectangularshaped key provided with a pair of notches on one set of opposed sides of said key and when said key is depressed the upper edges of each of said pair of opposed notches engage said first switch contact on opposite sides of said stationary support and stresses said first switch contact thereagainst whereby the first switch contact is forced into engagement with said second switch contact at two spaced points to thereby close said electrical circuit, said first switch contact additionally functioning as a return spring for said key when the electrical circuit is open.
 2. The combination as claimed in claim 1 wherein said first and second contacts are secured within said keyboard, the latter having a plurality of openings provided with guides for respective corresponding keys, said guides provided with support members for said second switch contact and having said stationary support against which said first switch contact rests.
 3. The combination as claimed in claim 1 further comprising another pair of notches on the other set of opposed sides of said key which are deeper than the first pair of notches whereby when said key is depressed said first switch contact is forced by said first pair of notches into engagement with said second switch contact and the upper edges of said second set of deeper notches travels further downward until said stationary stop is abutted to form a stop for the downward movement of said key.
 4. The combination as claimed in claim 1, wherein the second switch contact is constituted by a second resilient member.
 5. The combination as claimed in claim 1, wherein said second switch contact is a fixed contact rod.
 6. The combination as claimed in claim 1, wherein said first and second contacts are positioned substantially perpendicular to each other.
 7. The combination as claimed in claim 4, wherein said first and second contacts are secured within said keyboard, and the latter is provided with a plurality of openings for a plurality of corresponding keys.
 8. The combination as claimed in claim 7, wherein said openings are provided with guides for the respective keys, said guides having first support members for said second switch contact and additionally being provided with second support members against which said first switch contact rests.
 9. The combination as claimed in claim 8, wherein the keys are each provided with lateral projections that snap into the adjacent guide thereby being movably retained therein. 